1. Field of the Invention
The present invention relates to information recording processors, information playback processors, methods therefor, and information recording media and computer programs used therewith. In particular, the present invention relates to an information recording processor, an information playback processor, and a method therefor in which, in a configuration capable of recording additional data, such as key information for use in decrypting content, content-playback control information, and copy-control information, on an information recording medium containing content, such as image data and music data, and reading the additional data, specific user control data included in recording data is set as additional-data storing user control data, and DC control bits set in a specific recording frame included in the recording data are set as pointer information representing the position of the additional-data storing user control data, whereby embedding of additional data that is difficult to analyze is realized. In addition, the present invention relates to a recording medium and computer program used with the information recording processor, the information playback processor, and the method therefor.
2. Description of the Related Art
When data, such as music data and image data, is recorded in digital form on a recording medium, recording processing is performed in accordance with a predetermined recording format. For example, error-detecting/correcting codes are added to original data to be recorded, and the data is recorded in a form in which it is coded to have a format adapted for specific data recording/playback processing.
Regarding an information recording medium enabling high-density information recording, recently, an information recording medium based on a system using a blue laser to perform information recording and playback has been developed. In information recording using the blue laser, processing that converts two-bit data into three-bit data is basically performed.
Types of content to be recorded on the above information recording medium include, for example, movie data and music data. In general, rights of distribution, etc., of many types of content, such as music data and image data, are owned by content creators or sellers. Therefore, in a common form for distributing the types of content, certain limitations in the use of the content are set, that is, by allowing only registered users to use the content, unauthorized reproduction, etc., are prevented.
On a mass-storage recording medium, such as a recording medium using a blue-laser recording system capable of mass-storage recording, for example, a data capacity corresponding to one to several movies can be recorded. Since content can be easily recorded as described above in the form of digital information, many problems such as the spreading of unauthorized copies occur, so that reduction in profit of the copyright holder and distributor of the content becomes a large problem.
A system for preventing such unauthorized use of content has been proposed. In this system, content to be recorded on an information recording medium is recorded in encrypted form, and, simultaneously, encryption-key information for use as an encryption key for the encrypted content, information forming partial data of the encryption-key information, encryption-key generating information, such as data (e.g., a seed) required for generating an encryption key, or control information of various types, such as content-playback control information and copy-control information, is recorded as secret information on the information recording medium. In addition, a playback-processing program executed in a playback apparatus of a user reads the secret information, such as a key corresponding to the content to be played back, decrypts the content in accordance with the read secret information, and allows use of the content in accordance with playback-control information.
Regarding an example of the related art which discloses processing using embedding of secret information, for example, Japanese Unexamined Patent Application Publication No. 2003-45128 discloses a technology in which special data is embedded by using margin bits of eight-to-fourteen modulated data. Japanese Unexamined Patent Application Publication No. 2002-367282 discloses a technology in which, in a system using transformation tables for modulating processing, data concerning one transformation table, which is used in modulation, is extracted and additional data is acquired based on the extracted data.
However, if the user or an authorized user of content acquires information representing the position of such an encryption key or control information on the information recording medium, that person can leak or alter the additional data. For example, a problem occurs, that is, information or copy-control information may be altered, or key information may leak out. Leaking of the encryption key or alteration of the control information will break a content-utilization form based on the valid right to use content, so that it is difficult to sufficiently protect the copyright of the content and the right to use the content.